slight leak from sink drain trap on Swift - under van

[chrisT70]

noticed for first time we have a slight leak when using the bathroom sink in our 2006 swift sundance. it appears to be coming from the round black trap under the van which connects the sink drain to the waste grey tank.
i have unscrewed the "lid" to the round black trap, and altho not blocked or anything, but it does leak when using the sink, hadnt noticed before as we had stayed on grass pitches, last weekend after leaving a hardstanding i found a large wet patch!
I am fairly sure i can sort this myself but should the drain cap have some sort of seal as it didnt appear to have anything?
i intend stripping the unit out and having a proper look as to why its leaking as its only held in with a couple of clips on the drain hoses etc. any help or advice appreciated.

 

[caspar]

Mine has, but don't know if they all do.

 

[David & Ann]

I would get a plastic tax disc holder. cut out the shape and use as a seal. That solved my leaking problem from under the sink. I did not have a seal originally. It must be wafer thin.

 

[chrisT70]

thanks for that, will try a seal in there. suspect it should originally have had something as the plastic lid isnt overly tight when you screw it back onto the body, quite easy to get on/off.

 

[Martinsouthwales]

Washers

If you find you need a thicker washer than a tax disc holder, try getting an old car inner tube from a tyre dealers. They make brilliant washers of all kinds. Make sure you use a part of the tube without a seam on.

 

[David & Ann]

You may find that you never did have a washer in there. Just wear and tare. Like Martinsouthwales said if the plastic tax disc does not do the trick then go for the rubber tube. Important you don't force it to fit.